Refrigerator alarm system



Jan. 9, 19,51 c. A. s'ncKEl.

REFRIGERATOR ALARM SYSTEM Filed NOV. 19. 1946 2 Sheets-Sheet 1 :WIL

NNKATWN IN VEN TOR.

A. sm/fc/ Wwf Jan. 9, 1951 c. A. STICKEL REFRIGERATQR ALARM SYSTEM 2 Sheets-Sheet 2 Filed Nov. 19, 1946 Insulation ramadan. '9, 195.1 2,537,431

UNITED s'rAras PATENT ori-lcs Carl'A. Stickel, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Y Application November 19, 194B, Scrill N0. 710,733

l 23 Claims. (0l. 177-811) 2 This application is a continuation in part of sure controlled signalingvdevice which will renmy copending application S. N. 504,527, filed der the signaling device inoperative under cer- Octoberl, 1943, now abandoned. tain initial conditions under which the proper This invention relates to temperature and/or temperature and/or pressure is not maintained pressure control devices by which the temperaand thereafter be restored automatically to its ture and/or pressures in any room, compartnormal eifectiveness upon the restoration of ment, space or system is maintained below or normal conditions. above a certain limit and in which a signal or It is another object of my invention to provide some othersuitable indication is given automatia cycling temperature and/or pressure control 'cally in case the temperature and/or pressure 1 with a signaling device which' may be manually exceeds the desired limit. Such control device rendered ineiective and which will remain so may be used, for example, for refrigerating apuntil the end of a cycle, after which its effectiveprtu, 01' heating Systems. and for pressure ness wiliberestored automatically. systems. A It is also an obJect of my invention to provide I have chosen to illustrate my invention as ap- 9, signaling system for temperature and/r pres. plied t0 refrigerati irlsice crea-m, @Btg li controls in which audible devices may be frozen food cabinets w e necessary satisfactorily, Prevmt the cabinet from-'Warming t0 Such an It is another object of my invention to provide extent thai the frozen PlOduGtS mit Such a control device with an additional control cabinets have been provided with signaling deswitch which at any time may be rendered m. vices of various tylie- The Riley Patent effective but be rendered effective upon a pre- 2,092,085, for example. shows a form of control scribed operation of the control device and signaling device for refrigerators wherein a It is another object of my inventionto mm Warning light is lighted Whenever the tempera? vide a control for an electrically operated systure of the cabinet exceeds a certain limit. tem with a signaling device which may be mam n ha been found that with such an me' ually rendered ineffective and will remain so ment either dung-the mmm operation of until the supply of electrical energy to the sysapparatus or whenever such apparatus is tem is interrupted after which its eiectiveness with an unusually large amount of food that the wm be restored auwmaticany temperature of such cabinet will rise above the Further objects and advantages of the pres desired temperature limit and the signal light ent invention will be apparent from the following will light and remain lighted for comparatively description. reference being had to the accom long periods of time until the refrigerating syspartying drawings, wherein a preferred form of tem has operated longenough to cool the conthe present invention is clearly Shown ents of the cabinet to the proper temperature. Y In the drawings. y f is c au of this time ht, rensgemtlggdsisa Fig. l is a view partly in section of a control perating properly an ere no n c a semcemam This situatmn is even more disfor a frozen food refrigerating system provided turbing where an audible device. such as a illl ghiesmn system embOdYinE One form 0f h e iellsligaltarggngngemof filling@ geaurs, Fig. 2 is a fragmentary sectional view similar which would be so disturbing as to preclude the to ris. 1 showing the signanng control held in use of an audible signaling device. -This also :nntilffiesciij 315mm. hi: herllrxiseration maylge sumclntiwedexhtgus-gebslmpowg; oFig 3 is a fragpmentary sectiopxal View illussupp norm y D power independent of the electrical power supglr'tisitggigg'iggolge Signaling control from s ould be 211i; nleuufgur n imsraltlfelyrge above Fig. 4 is a view partly in section, of a control normal. To disconnect the battery with an ordifor a frozen food -refrigerating system provided nary manually oprated' gwn-:l s undesiable 50 grits; insignalltisystem embodying another form th witch were o reven opxiotont of etle signaling deince it isllikely that Fig. 5 is a fragmentary sectional view similar people would forget to reclose the switch. to Fig. 4 showing the signaling control held It is therefore an object of my invention to in ali ineffective position While electric elilveii?v iS provide a control for a temperature and/or pres- 66 being supplied to the system; and

Fig. 6 is a fragmentary'sectional view showing the detent.

Referring now to the drawings, there is shown in Fig. 1 a sealed motor-compressor unit 28 which delivers compressed refrigerant to a condenser 22 where the refrigerant liquees and is forwarded under the control of a liquid control device or restrictor 24 to an evaporator 28 which surrounds the frozen storage compartment 28 of .a frozen storage cabinet 88. The operation of the refrigerating system is controlled by a refrigerator control 82 which includes a metal bellows 84 connected by capillarytubing 88 to a bulb 88 or similar device which is positioned in heat exchange relation with the walls of the frozen storage compartment 28 and the evaporator 26. The bellows 34 operates a primary lever 48 provided at one end with a double toggle type of snap-acting mechanism including a secondary lever 42 and a toggle spring 44 which connects to a post 48 of the control lever 48. The control lever 48 is pivoted upon a pin 58 and controls the control device proper which in this case is a set of switch contacts 82 and 54.

The switch contact 84 is provided at the top of the bonductor post which is connected to one of the supply conductors 58 while the switch contact 52 is mounted upon the end of a spring fastened to another conductor post which is connected by the conductor 58 to the sealed motorcompressor unit 28 which in turn is connected to the other v supply conductor 88. The spring which holds Athe contact 52 is tensioned so that in its unstressed condition it carries the contact 52 away from the contact 84, so that when the control lever 48 is turned in a counter-clockwise direction placing the post 48 in contact with the differential adjusting screw 82, the contacts 82 and 84 will be separated.

The position of the set-screw 82determines the temperature and/ or pressure differential between the opening and closing of the switch contacts 82 and 54. The temperature` at which the opening and closing takes place is determined by the range spring 84 which may have its tension adjusted by the range adjusting screw and knob 88 (in order to change the temperature at which the switch 52 and 54 is opened and closed. The bulb 38 is charged with a volatile liquid which will create a vapor pressure within the bellows in proportion to the temperature of the bulb 88 and the compartment 28. As an alternative the bulb 88 may be iilledwith an absorbent such as activated charcoal and the bulb and bellows filled with a gas which may be absorbed and evolved by the.

charcoal in accordance with changes of temperature in the bulb 88 and the compartment 28. By this arrangement, the movement of the primary lever 48 is a function of temperature.

This function has been taken advantage of to provide a signaling control by placing a signaling contact 88 in a position wherein it will be contacted by the primary lever 48 when the temperature of the frozen storage compartment 28 reaches a prescribed value. This contact 58 is supported at the end of a. thin spring metal strip 18 which is tensioned so that it will normally remain in a straight position against the set-screw I8l. It is anchored in an insulating support between the insulating member 12 and an insulating spacer 14 which are connected to the frame 18 of the control 82. ,The strip 18 is connected in the signaling circuit by the conductor 'I8 which connects to a set of dry cell batteries 88 or other suitable power source which in turn is connected or a buzzer. The signaling device 82 is connected in series with a manual switch 84 which in turn l is connected by the conductor 88 to the frame 18 of the control 32 which connects to the primary lever 48. The manual switch 84 may be omitted ii desired to reduce the cost of the signalling circuit. i

. Although the bulb is not placed directly in the compartment 28 it will reect the temperature of compartment 28 even though the refrigerating system is operating, since,` it is placed at the discharge end of the evaporator 28 wherein the temperature of compartment 28 will be reflected in the temperature of the vapor leaving the evaporator 28. It will therefore be seen that even though the switch contacts 82 and .54 are closed and the refrigerating system is in the proper order and operating properly, that when considerable quantities of warm food are placed into the compartment 28 to be frozen, the temperature of the compartment 28 will rise above the maximum desired temperature of the cabinet which may be 5 or 10 F. Under such conditions the primary lever 48 will move against its stop 88 and it would also contact the contact 88 to close the alarm circuit. The signaling device 82v f would commence to operate providing an audible warning which would continue until the compartment 28 was reduced below 5 or 10 F. To keep the cost of such systems within the means of the average buyer the condensing unit is small and this temperature level may not be reached for a considerable time and the ringing of a bell or even the lighting of a light for that period would be objectionable.

Therefore upon the end of the strip 18 I have provided a small operating lever 88 which extends through a slot 82 in the outer case 84 of the control. This slot 82 limits the movement of the lever 8 8.' The case 84 may be provided with legends On and Oif. The moving of the lever 88 to the oi position raises the contact 88 away from the primary lever 48 when the primary lever 48 is in its uppermost position against the stop 88 illustrated by dot-dash lines in Fig. 2. In order to hold the contact 88 in this position during the time the refrigerating system is operating to reduce the food storage compartment down to its proper level, under such conditions I provide an extension 88` upon the control lever 48 in the form of a nose and I provide a spring latch .or detent 88 upon the end of the spring strip 18 so that when the control lever 48 is inthe closed circuit position the spring latch or detent 88 may be brought past the nose 86 as shown in Fig. 3 and will rest on top of the nose 86 as shown in Fig. 2 in order to `hold the contact 88 out of the path of the primary lever 48. This will hold the lever 88 and the contact-88 in its 05" or inoperative position as shown in Fig. 2 as long as the switch contacts 52 and 54 remain closed to continue operation of the refrigerating system.

When the refrigerating system finally brings the frozen storage compartment 28 down to its proper temperature the primary lever 48 will be lowered sufiiciently that the secondary lever 42 will be brought below the center line of the spring 44 and the control lever 48 will snapl in a counterclockwise direction to a position placing the post 48 against the differential set-screw 82 as shown in dot-dash lines. This will stop the refrigerating system. The nose 88 being a part of the control lever 48 will be similarly moved'as illustrated in dot-dash lines, so that it will move or detent 88 allowing the away from the latch Y back to the position spring strip 18 to Sllxins` Vshown in Fig. 1 against the adiusting screw lill as to raise or lower the-temperature at which the contact 89 is contacted by the primary lever 48 to open and close the alarmcircuit. While I prefer *that the spring latch 98 be resilient as shown, so that it may pass the 'nose 98 without moving the nose- 88 it may be made rigid, it desired, in which case it will force the nose 98 to retract a sulcient distance against the tension of the toggle spring 44 to permit its movement in either direction. The surfaces o! spring latch or detent 98 which contact lthe nose 98, are beveled so that they present a resilient V projection pointed toward the nose 98 which may be forcibly cammed past the nose 98 in either direction and yet will be supported by the nose 98 as shown in Fig. 2.

Through this control whenever the frozen storage cabinet is loaded with warm food the bellows 8i will expand and the primary lever I9 will rise and move the control lever I8 to the iull line position as shown in Fig. l, closing the contacts 82 and 5l and causingthe operation of the refrigerating system. .The signal alarm circuit in a short time, will be closed by the continued exacens:

pansion of the bellows 94 to place the primary lever I9 into contact with the contact 88. At any time after the switch contacts 82 and 58 are closed the lever 90 may be pushed to the right as viewed in Fig. 1, to raise the contact 88 out of the path 6 position whenever'the motor circuit ot the refrigerating apparatus is deenergized.

Referring now more particularly to Fig. 4, there is shown a U-shaped bimetal holding member |98 having its lower end II'I curled. upwardly sc that when in the heated position shown, it will hold the detent 98 as shown in Fig. 5. when the lever |98 is moved to the oit position. The U-shaped blmetal member |88 replaces the nose 98 which is omitted from the control member |48 in the second modification. This U-shaped bimetal member |98 has its rear leg lconnected by the bolt 998 to the supply conductor 981. The i'ront leg 989 is connected` by the bolt 8i I 'to the conductor 8I8 which connects to the stationary contact 8l. The movable contact I8 is connected by the conductor lll with the normally closed thermal overload protector 8H,

which opens the circuit of the 4motor-compressor unit 29 under anyoverload condition to prevent damage to the motor windings. The motor-compressor unit 20 is connected to the other side of the electrical supply source by the conductor 8i9.-

The bimetal |98 is so constructed that it quickly assumes the full line position shown in Figs. 4 and 5 when heated by the motor current. The thlcknessof the bimetal is exaggerated in the drawings. Should the motor circuit of the sealed motor-compressor unit 28 be interrupted for any reason whatsoever, the bimetal |98 will bow to the left to the dot-dash line positions shown in Figs. 4 and 5. If the'lever |98 has been in the of the primary lever and to place lthe detent 98 on top of the nose 98 as shown in Fig. 2. This will open the alarm circuit and prevent or stop the operation of the alarm 82. The contact 88 and the lever 90 will be held in this position until the compartment 28 is brought down to its proper cut-oil temperature at which temperature the switch contacts 52, 8l will be opened and the refrigerating system stopped.

In the opening of the contacts 82, 8l the spring 84 will pull the primary lever 48 downwardly causing the snap-acting mechanism tp trip the control lever 48 to the opencircuit pomtion carrying the nose 98 away from the detent 98 to place the alarm contact 88 in position, as shown in- Fig. 1 to perform its normal function of giving a warning whenever the temperature of the compartment 28, as reilected by the positiion of the primary lever 48, reaches the prescribed limit carrying the primaryV lever 48 into contactdwith the contact 88 to close the alarm circuit and ring the bell 82. v

In the second modiiication disclosed in Figs. 4, 5 and 6 the refrlgerating system as well as the following parts of the control' system, Such as the bellows, primary lever, the double toggle snapacting lever and spring, the range spring and its adjusting screw and knob. the strip 10, the contact 88, the nose 98, the adjusting screw IBI, as well as the alarm circuit, are the same as the iirst modification and have the same reference characters. The second modiilcation diii'ers from the ilrst modification in that instead -of the restoration of the alarm lcontact 88 to ,its normal effective position being dependent upon the opening of the switch contacts '52 and Il as in Figs. l to 3, the second form shown in Figs. 4 to 6 makes the restoration electrically responsive to allow the alarm contact 88 to return to its normal effective off or latched position, the bowing of the bimetal |98 to the dot-dash line position will release the detent 88 and allow the strip 19 and the contact' 88 to move to its normal eiiective position with the strip 18 against the stop screw |0I.

vThus in this form, should the connection with the source of power supply be broken, such as for example, by the accidental removal of the plug connection, or perhaps by the tripping of the -overload 9H, or by failure of the power supply, or by the opening of the contacts M and 88, the signal alarm will be restored to its normal .eilective condition. Should the temperature of the compartment 28 be above the maximum desired temperature the signal alarm circuit will be energized, since the primary lever will rise sumciently to make contact with the contact 88 to give the warning that the temperature is not being maintained. Thus in this second modiilcation the signalalarm is returned to eiective condition, not only when the contacts 54 and 58 open, but also whenever the electrical circuit is deenergized for any reason whatsoever.

While I have illustrated my alarm control as applied to a refrigerating system, since the primary lever 48 is both temperature responsive and pressure responsive due to the pressure within the bulb, it may be applied to other pressure and temperature applications by connecting the bellows to the source of pressure or to the temperature condition which is to be controlled. The contacts 52, 5I may be used to control the means for changing the temperature or pressure to maintain the desired limit.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other liorrris might be adopted, as may come within the scope of the claims whichl follow.

What is claimed is as follows:

1. In combination, a ilrst means to be kept within desired temperature limits, a temperature changing means for maintaining the first means within said temperature limits, a cyclically operable control means for said temperature changing means having a predetermined differential providing operating and idle periods corresponding to said temperature limits, a signaling device, means ior rendering effective said signaling device when one oi said temperature limits is exceeded, and releasable means controlled fby said cyciically operable means for preventing the signaling device from being rendered eilective only until the termination of one of said periods of operation of the temperature changing means.

-2. In combination, a cabinet to be kept below a desired temperature, a refrlgerating system for cooling said cabinet, a cyclically operable control means providing operating and idle periods of said refrigerating system for maintaining said cabinet below said temperature, a signaling device, means i'or operating said signaling device when said temperature is exceeded, and settable releasable means for preventing the operation of said signaling device during any one of said operating periods until the termination of said period only.

3. A rst control comprising a control device operable to rst and second control positions", an actuating means for operating said iirst control ldevice to and from said iirst and second positions, a second control device operated by said actuating means to first an second control positions, an electrical circuit connected to said second control device, manually settable means for deenergizing said electrical circuit, and means responsivcto the operation of said ilrst control device from one position to another for releasing said settable means.

4. A control comprising a ilrst control`device operable to iirst and second control positions, an actuating means for operating said first control device to and from said iirst and second positions, a second control device operated by said actuating means to first and second control positions, manually settable means cooperating with said rst control device for holding said second control device in one o! its positions'when said first control device is in one of its positions, said ilrst control device being provided with means for releasing said settable means coincidentally to its operation from one control position to another.

5. A control comprising a first control device operable to first and second control positions, an actuating means for operating said ilrst control device to and from said first and second positions, a second control device in the form of switch contact means operated by said actuating means to open and closed positions, manually settable means cooperating with said first control device for holding said switch contact means in one of said positions when said first control device is in one of its positions regardless of the movement of said actuating means, said first control device being provided lwith means for releasing said manually settable means coincidentally to its operation from one control position to another.

6. A first control comprising a control device operable to and from iirst and second control positions, an actuating means for said first control device, a snap-acting means for connecting said actuating means and said control device, a second control device in the form of a switch contact means operable to one control position upon abnormal movement of the actuating means and to a second position upon normal movement ot the actuating means. a manually operable means..

' 7. A control comprising a control device operable to ilrst and second positions, an' actuating means for operating said control device to and from said nrst and second positions. a switch means operated by said actuating means to closed and open positions, manually settable latching means for holding said switch means in the open position, and means responsive to the operation of said control device from one position to another for releasing said settable latching means.

8. A control comprising a iluid motor, a ilrst control device connected to and operated by said fluid motor to iirst and second control positions, a second control device operated by said iluid motor to ilrst and second control positions, a detent connected to and moved by said iluid motor to first and second positions coincidentally to the operation o! said rst control device, said second control device being provided with a manually settable latching means cooperating with said detent when in one of its positions for holding the second control device in one of its positions and i'or preventing normal operation of the second control device until said detent is moved i'rom said one position.

9. A control including a control means operable to and from first and second control positions, an actuating means for said control means, snap-acting means for controlling the operation of said actuating means and said control means, a control device operated to a tlrst position by said actuating means upon movement to an abnormal position and operable to a second position upon all normal movements of said actuating means, a manually settable device for preventing the operation oi.' said control device to its ilrst position, and means responsive to an operation or one o! said means for releasing said manually settable means to restore the normal control oi.' said control device.

10. In combination, a tlrst means to be kept within desired temperature limits, a temperature changing means for maintaining the first means naling device ineffective regardless of temperature conditions for one of said periods including means responsive to the termination of said one period for restoring said signaling device to potential eifectiveness tor giving a warning should one oi.' the temperature limits be exceeded.

11. In combination, an electrically powered means to be kept within' desired limits, means for supplying said ilrst means with electrical energy, control means for interrupting and completing the supply oi' electric energy to said electrically powered means to provide idle and operating periods, a signaling device, means for rendering said 9 device effective to give a warning signal when one of said limits is exceeded, means for rendering said signaling device ineffective for one of said periods only including means operv able coincidentally to the interruption o1' the supply of electric energy for restoring said signaling device to normal potential eiiectiveness to give a warning should one of the limits be exceeded.

l2. A control comprising a uid mo r means, a iirst movable device connected to nd operated by said fluid motor means to first and second operating positions, a second movable device having two physical positions, said second devicer in the first of said physical positions being operated by said fluid motor means to first and second control positions, a detent means for holding said second device in the second physical position for preventing its operation to its second control position, said detent means including means operable coincidentally to the operation of said first device from its first operating position to its second operating position for releasing said second device, said second control device including a biasing arrangement for biasing it from the second physical position to the ilrst physical position.

13. Incombination, a ilrst ymeans to be kept within desired temperature limits, a temperature changing meansfor maintaining the ilrst means within said temperature limits, a cyclically operable controlvmeans for said temperature changing means having a predetermined differential providing operatingaand idle periods corresponding tosaid temperature limits, a signaling device, means for rendering effective said signaling device when one of said temperature limits is exceeded. settable means for preventing the signalingldevice from being rendered effective, and

. means responsive to the next succeeding cycling operation of the control means for releasing said settable means.

14. In combination. a cabinet to be kept belowl for cooling said cabinet, control means for starting and stopping the operation of said refrigerating system providing operating and Iidle periods, a signaling device, means for operating said signaling device when said temperature is exceeded,

land settable releasable means for preventing the Aoperation of said signaling device during one of said periods until the termination of said period only, including means operable coincidentally to the stopping of said refrigerating system for restoring the signaling device to its normal potential effectiveness to give a warning should one of the limits be exceeded.

16. A control comprising a fluid motor, a first control device connected to and operated by said fluid motor to first and second control positions,

a second control device operated by said iluidA motor to first and second control positions, an electrically controlled detent movable to first and second positions, said second control device being provided with a manually settable latching means cooperating with said detent when in onel of said positions for holding and preventing normal operation oi' said second control device in one of its positions, said first control device being provided with electrical control means electrically connected tol said detent for controlling said detent to release said second control device.

17. A control comprising a first control device operable to rstand second positions, a second control means operable to ilrst and second positions. settable holding means for holding said second control means in the rst position, and means responsive to the operation of said iirst control device from one position to another for releasing said settable holding means.

18. A control comprising a rst control device operable to iirst and second positions, a second control device operable to rst and second positions, said second control device including means for biasing it from the second position to the lirst position, means for operating said first and second control devices to and from their first and second positions, settable holding means for holding said second control device in its first position to prevent it from being operated to its second position,.and means responsive to the operation of the rst control device from one position to another for releasing the settable holding means. Y

19. A control comprising a first movable device operable to first and second operating positions, a second movable device having first and second physical. positions, means for operating said second movable device when in the first physical position to first and second control positions, .settable holding means for holding said second device in said second physical position for preventing its operation to its second control position, said holding means including means operable coincidentally to the operation of the first movable device from its first operating position to its second operating position for releasing said second movable device.

20. A control comprising a first movable device operable to first and second operating positions. a second movable device having first and second physical positions, means for operating said second movable device when in the first physical position to first and second control positions, settable holding means for holding said second device' in said second physical position for preventing its operation to its second control positiom said holding means including means operable coincidentally to the operation of the first movable device from its rst operating position to its second operating position for releasing said second movable device, said second movable device including a biasing arrangement for biasing it from the second physical position to the first physical position. l

2l. In combination, a first means to be kept within desired temperature limits, a temperature changing means for maintaining the first means within said temperature limits, a cyclically operable control means for said temperature changing means having a predetermined differential providing operating and idle periods corresponding to said temperature limits, a signaling device, means for rendering effective said signaling device when one of said temperature limits is exceeded, settable means having an ineffective position in which it is inoperative to affect the operation of the signaling device and an eifective position vfor preventng the signaling device from being rendered effective, and means responsive to the next succeeding cycling operation of l1 the control means for causing the movement of the settable means from the effective to the inef- Iective position.

22. A control comprising a ilrst control device operable to first and second positions, a` second control means operable to iirst and second positions, settabie means having an ineilective position in which it is inoperative to affect the operation of the second control means and an eilective position for holdingy the second control means in the ilrst position, and means responsive to the' operation of said` first control device from one position to another for causing the movement of the settable means from the effective position to its inenective position.

23. A control comprising a first movable device operable to first and second operating positions, a second movable devicehaving iirst and second physical positions, means for operating said second movable device when in the first physical position to rst and second control positions, settable means having an ineffective position in which it is inoperative to ailect the operation of the second movable device and an REFERENCES CITED The following references are of record in the ille ot this patent:

UNITED STATES PA'IEN'IS Number Name. 4 Date 1,066,731 Jaynes ...'--.July 8, 1913 1,969,304 Grooms Aug. 7, 1934 2,092,085 Riley Sept. 7, 1937 2,115,027 Leonard Apr. 26, 1938 2,447,893 Bauman Aug. 24, 1948 2,447,894 Bauxmm` Aug. 24, 1948 2,447,895 Bauman Aug. 24, 1948 Certificate of Correction Patent No. 2,537,431 l January 9, 1951 CARL A. STICKEL Itis hereby certified that error appears in the printed speccaton of the above numbered patent requiring correction as follows:

Column 7, lines 27 and 69, respectively, for the Words rst control comprlsing a control read control comprising a first control;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 27th day of February, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,537 ,431 January 9, 1951 CARL A. STICKEL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 7, lines 27 and 69, respectively, for the Words first control comprlsing a control read control comprising a first control;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed this 27th day of February, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Uommzssz'oner of Patents. 

